WASHINGTON -- Pollution from Asia is helping generate stronger storms over the North Pacific, according to new research. Changes in the North Pacific storm track could have an impact on weather across the Northern Hemisphere. Satellite measurements have shown an increase in tiny particles generated from coal burning in China and India in recent decades, researchers report in Tuesday's issue of Proceedings of the National Academy of Sciences.

The team, led by Renyi Zhang of Texas A&M University, studied pollution and clouds between 1984 and 2005, concluding that increasing particles enhanced the cloud updraft to generate more intense thunderstorms than previously.

Comparing 1984-1994 with 1994-2005 they found an increase of 20 percent to 50 percent in deep convective clouds.

The Pacific storm track, they noted, plays a critical role in global atmospheric circulation, and altering this weather pattern could have a significant impact on the climate.

"The intensified storms over the Pacific in winter are climatically significant," the researchers wrote. "The intensified Pacific storm track can also impact the global general circulation."

A particular threat, they added, is the potential for increased warming of polar regions.

The research was supported by National Science Foundation, Department of Energy and the National Aeronautics and Space Administration.

In another report in the same issue of PNAS, researchers said that in addition to protecting the ozone layer, the reduction on ozone-depleting chemicals has slowed the rate of global warming.

The Montreal Protocol, signed in 1987, led to a reduction in chemicals released into the atmosphere in an effort to preserve the ozone layer that screens out many of the sun's damaging rays.

Those same chemicals are also potent contributors to greenhouse warming, and their reduction has resulted in a slowdown in global warming, according to a team led by Guus J. M. Velders of the Netherlands Environmental Assessment Agency. The savings in trapped heat are equivalent to about 10 years of growth in carbon dioxide concentrations, they estimated.

Joining Velders in that study were researchers from the U.S. Environmental Protection Agency, National Oceanic and Atmospheric Administration and DuPont Fluoroproducts.